Specific inhibition of oxygenase activity of ribulose-1,5-diphosphate carboxylase by hydroxylamine

Discoveries in Rubisco (Ribulose 1,5-bisphosphate carboxylase/oxygenase): a historical perspective

Historic discoveries and key observations related to Rubisco (Ribulose 1,5-bisphosphate carboxylase/oxygenase), from 1947 to 2006, are presented. Currently, around 200 papers describing Rubisco research are published each year and the literature contains more than 5000 manuscripts on the subject. While trying to ensure that all the major events over this period are recorded, this analysis will inevitably be incomplete and will reflect the areas of particular interest to the authors.

Molecular and cellular regulation of autotrophic carbon dioxide fixation in microorganisms

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CU(II)-dependent inactivation of Mn-catalase by hydroxylamine

Hydroxylamine is a strong inhibitor of the Mn-catalase of Lactobacillus plantarum in the presence of hydrogen peroxide [Kono, Y., and Fridovich, I. (1983) J. Biol. Chem. 258, 13646-13648]. In the presence of CuCl2 the Mn-catalase was rapidly inactivated by hydroxylamine without the addition of hydrogen peroxide. FeSO4 and MnCl2 were approximately 10% and 4% as effective as was CuCl2. Under anaerobic conditions, the inactivation did not occur. The chelating agents such as EDTA and histidine completely prevent the inactivation. These results indicate that the hydrogen peroxide produced during the autooxidation of hydroxylamine catalyzed by CuCl2 participates in the CuCl2-dependent inactivation by hydroxylamine.

Inhibition of ribulose-1,5-bisphosphate carboxylase-oxygenase activities by hydroxylamine

Hydroxylamine directly and reversibly inhibits both activities of homogeneous ribulose-1,5-bisphosphate carboxylase-oxygenase (3-phospho-D-glycerate carboxy-lyase (dimerizing), EC 4.1.1.39) isolated from diverse sources. NH2OH is an uncompetitive inhibitor of carboxylase activity with respect to ribulose-bisphosph ate. This reagent also reacts non-enzymically with ribulosebisphosphate to deplete this substrate. Contrary to previous reports, these results indicate that hydroxylamine directly and indirectly inhibits both activities of this bifunctional enzyme.

Differential effects of metal ions on Rhodospirillum rubrum ribulosebisphosphate carboxylase/oxygenase and stoichiometric incorporation of HCO3- into a cobalt(III)--enzyme complex

Mg2+ or Mn2+ ions supported both the carboxylase and oxygenase activities of the Rhodospirillum rubrum ribulosebisphosphate carboxylase/oxygenase. For the carboxylase reaction, Mn2+ supported 25% of the maximum activity obtained with Mg2+; oxygenase activity, however, was twice as great with Mn2+ as compared to that with Mg2+. A further differential effect was obtained with Co2+. Co2+ did not support carboxylase activity and, in fact, was a strong inhibitor of Mg2+-dependent carboxylase activity, with a Ki of 10 microM. Co2+ did, however, support oxygenase activity, eliciting about 40% of the Mg2+-dependent oxygenase activity. No other divalent cations supported either activity. With high concentrations of Mg2+ or Mn2+, maximum carboxylase activity was seen after a 5-min activation period; activity decreased to about half of maximum after 30-min activation. A similar time dependence of activation was observed with Mn2+-dependent oxygenase activity but was not seen for Mg2+- or Co2+-dependent activity. Both carboxylase and oxygenase activities were inactivated by the oxidation of Co2+ to Co(III) with the resultant formation of a stable Co(III)--enzyme complex. In the presence of HCO3- (CO2), Co(III) modification was stoichiometric, with two cobalt atoms bound per enzyme dimer. Carbon dioxide was also incorporated into this Co(III)--enzyme complex, but only one molecule per enzyme dimer was bound, indicative of half-the-sites activity. These results thus indicate that there are substantial differences in the metal ion sites of the carboxylase and oxygenase activities of R, rubrum ribulosebisphosphate carboxylase/oxygenase.

Mutations altering the catalytic activity of a plant-type ribulose biphosphate carboxylase/oxygenase in Alcaligenes eutrophus

Use of a bacterial system has allowed the isolation of several mutationally altered species of ribulose-1,5-bisphosphate carboxylase/oxygenase having a wide range of catalytic activities. Biochemical and serological techniques were used to classify the mutant strains into three groups: (1) no detectable ribulose-1,5-bisphosphate carboxylase/oxygenase protein present (both subunits missing); (2) mutant strains having ribulose-1,5-bisphosphate carboxylase/oxygenases with lowered specific activities; and (3) mutant strains producing large quantities of catalytically inactive ribulose-1,5-bisphosphate carboxylase/oxygenase.

The effect of divalent metal ions on the activity of Mg(++) depleted ribulose-1,5-bisphosphate oxygenase

Ribulose-1,5-bisphosphate carboxylase-oxygenase is deactivated by removal of Mg(++). The enzyme activities can be restored to a different extent by the addition of various divalent ions in the presence of CO2. Incubation with Mg(++) and CO2 restores both enzyme activities, whereas, the treatment of the enzyme with the transition metal ions (Mn(++), Co(++), and Ni(++)) and CO2 fully reactivates the oxygenase: however, the carboxylase activity remains low. In experiments where CO2-free conditions were conscientiously maintained, no reactivation of RuBP oxygenase was observed, although Mn(++) ions were present. Other divalent cations such as Ca(++) and Zn(++), restore neither the carboxylase nor the oxygenase reaction. Furthermore, the addition of Mn(++) to the Mg(++) and CO2 preactivated enzyme significantly inhibited carboxylase reactions, but increased the oxygenase reaction.